Area Code 321 covers all of Brevard County, but in addition it also is an entire overlay for Area Code 407.
Example: Orlando is both area codes 407 and 321.

Michigan (2) :

The city of Livonia is area code 734, but surrounding areas that use Livonia as a mailing address are located in the 248 and 313 area codes.

New York (3) :

Area code 917 is predominantly cellulars and pagers in New York City. Some regular lines in Manhattan have recently been assigned the 917 area code. The new overlay area codes of 347 and 646 have also been assigned cellulars and pagers, in addition to regular land lines.

Oregon (4) :

Area Code 971 does not overlay Clatsop and Tillamook Counties. These areas are entirely served by Area Code 503.

Texas (5 and 6) :

Area Codes 713/281/832:

The introduction of area code 832, in the form of an overlay, officially erased the 713 and 281 area codes. To date, a majority of the 713 and 281 area codes are assigned to specific areas.
713 - Bellaire, Galena Park, Houston, Jacinto City, Pasadena, South Houston, and West University Place.
281 - Alvin, Baytown, Deer Park, Humble, Katy, La Porte, League City, Missouri City, Pearland, and Sugar Land.
While a majority of Houston is area code 713, some sections of the city are located in area code 281.